(1) Field of the Invention
The invention relates to a stator core for an electronically commutated DC motor with an internal rotor. The stator has a plurality of radially inwardly directed pole cores which at their periphery are integral with back iron segments, and the back iron segments are integral with adjacent back iron segments.
(2) Description of Related Art Including Information Under 37 CFR 1.97 and 1.99
A generic stator core is known from DE 10 2010 043 976 A1 in which the back iron segments are connected together by compression regions arranged between the back iron segments lying opposite one another within an outer circle described by the latter. A stator core is supposed to be provided by the described arrangement of the poles of which, in particular pole pieces of which, are spaced a greater distance from each other. The increased distance serves to simplify the winding of the poles when using a needle winding method and to increase the number of turns of the stator winding, thus increasing the torque that can be achieved. By the use of compression areas, considerable forces are necessary after winding to reduce the diameter of the stator core and to reduce the increased distances between the poles and the pole pieces. The amount of force may use damage to the stator core. Using stator laminations could cause current bridges to be formed by mechanical deformation, for example, which favor the formation of eddy currents, resulting in loss of efficiency. Another disadvantage is that, during the pressing process, the back iron segments must be properly handled to obtain a defined reproducible final geometry.